We put in a dry hydrant when we built the pond, figuring doing it at the same time would cost a little less. We installed the recommended "bench" in front of the hydrant for hose support and situated gates in two fence rows to try and accomodate firetrucks. In (nearly) four years we have been unable to get the local FD to come out and test/try it - the dry hydrant clinic we attended said it should be back-flushed and test pumped once a year. No break on home insurance either; even though it's 200 yds from the house, it's not located "on an improved road."
When I think about it I wonder if (in our situation) we should have bothered - I guess it's something we did to try and mitigate fire risk, hope I never find out if it will help.